Traditionally, UV fluorescence spectroscopy is conducted using a single UV source and a mechanically swept sensor for measuring the emitted light. Recently, many new low-cost UV-emitting LEDs have emerged, offering a broad variety of wavelengths ranging from about 280 nm up to and including visible blue light.
Some patent publications in the field include WO04070369A1, which relates to a method for determining and/or monitoring impurity states in different fluids by using crystalline inorganic semi-conductor diodes (LED) emitting a white light and injection light-emitting diodes emitting at least one infrared radiation (RED) and/or ultra violet radiation (UVED). The method uses, in particular, the modification of the emission spectrum of the white LED. Variations in the peak wave lengths, in the ratios of the peaks of the light-emitting injection in relation to the peak of the photoluminescence, in selective absorptions, in excitations on the fluorescence, in intensities of the peak wave lengths and in integral emissions are used in addition to comparison of data to the modified spectrum of the infrared emitter and/or the UV emitter. The variations are registered with the help of a fiber optic compact spectrometer or a similar receiver. This method is automatically calibrated if the ratio of the injection luminescence to the photoluminescence of the white LED for similar flowing current densities represents a diode specific constant. Exceptionally reliable economical sensors are produced and constructed in a fast manner according to said method and can be used in many methods associated with fluids, for example, in cleaning processes and chemical technology.
US2006192957A discloses a spectrophotometer for integration purposes, including a measurement head with an illumination arrangement including at least one light source for the illumination of a measurement object located in a measurement plane (M) under an angle of incidence of at least 45 degrees, with a pick-up arrangement for capturing the measurement light remitted by the measurement object under an angle of reflection of the essentially 0 degrees relative to the perpendicular of the measurement plane, a spectrometer arrangement with an entry slot for the spectral splitting of the measurement light received through the entry slot and captured and with a photoelectric receiver arrangement exposed to the spectrally split measurement light for conversion of the individual spectral portions of the measurement light into corresponding electrical signals.
It further includes an electronic control, which controls the light source and produces digital measurement values from the electrical signals generated by the photoelectric receiver arrangement. The light source is constructed as a flat cosine radiator and is positioned in such a way that its radiation lobe is essentially perpendicular to the measurement plane (M) and the distance of the light source from the optical axis of the pick-up arrangement is essentially the same as the distance of the light source from the measurement plane.
US2012001094A describes an apparatus for measuring fluorescence of potable liquids contained within an optical quartz cell includes a deep UV laser or a compact UV LED that generates a light beam. A UV blocking and visible light transmitting optical filter reduces out-of-band emission from the LED. The optical quartz cell is between a pair of plane mirrors so that light from the light source travels through it several times. A concave mirror collects a fluorescence signal and has a common optical axis with a lens. The common optical axis is normal to an optical axis of the light beam. The concave mirror and lenses are positioned on opposite sides of the optical quartz cell. A fluorescence detector is in optical alignment with the concave mirror and the lens. Optical wavelength selection of the fluorescence emission uses optical filters or a spectrometer.
There is still a need to provide improved optical detection systems and methods.